PROJECT SUMMARY/ABSTRACT Maintaining emotional stability in the face of negative life experiences is critical for healthy aging. Maladaptive responses to negative affective stimuli (?NAffecS?) are implicated in psychiatric disorders, including major depressive disorder (MDD). In fact, there are shared brain regions involved in responses to NAffecS and MDD pathophysiology, including: hypothalamus (HYPO), amygdala (AMYG), hippocampus (HIPP), anterior cingulate cortex (ACC), and ventromedial, ventrolateral, dorsolateral, and orbital prefrontal cortices (PFC), areas that are among the most sexually dimorphic. Activity in this circuitry is physiologically associated with cortisol response, loss of parasympathetic cardiac tone, and immune responses, including TNF-?, IL-1?, IL-6, responses that differ by sex. We will test here that immune pathway abnormalities, beginning in fetal development, are associated with sex-dependent impacts on HYPO, HIPP, AMYG and PFC, resulting in maladaptive negative emotion processing and MDD in early midlife. Further, aging of NAffec circuitry (i.e., decline) into later midlife will be accelerated by MDD in early midlife, resulting in greater deficits in negative emotion processing in later midlife, that we predict will differ by sex, i.e. women worse than men. We are uniquely poised to examine this for the first time in humans using data from our prenatal cohort prospectively followed since 2nd/3rd trimesters and assessed at ages 44-50 in a previous NIH study, in which we investigated fetal programming of sex differences in MDD. We will re-recruit over 5 years 180 of these offspring (equally divided by sex; half with recurrent MDD) who, 11 years later, will be ages 55-61. We will relate maternal prenatal immune activity (TNF- ?, IL-1?, IL-6) to sex differences in NAffec circuitry deficits and maladaptive negative emotion regulation at ages 55-61 and decline from ages 44-50. We will use the same multimodal imaging approach as previously (structural, functional imaging (sMRI/fMRI)) coupled with hormones, autonomic and immune physiology, and emotion regulation measures. Novel transcriptomic analyses in the offspring's peripheral blood mononuclear cells will be used to measure abnormalities in innate immune gene expression in response to prenatal maternal immune exposures and related to adult midlife outcomes. Our lifespan perspective is an innovative approach to identify potential immunotherapeutic targets for maintaining healthy emotion processing that are sex-dependent and can be applied prior to functional decline. This will contribute to RDoC Negative Affect and Arousal phenotypes, physiology and genotypes, and impact of mood and sex.